This application is based on and incorporates herein by reference Japanese Patent Application No. 2001-36377 filed on Feb. 14, 2001.
1. Technical Field of the Invention
The present invention relates to a fuel injection nozzle for an internal combustion engine, such as a diesel engine, in which the nozzle is attached to each cylinder of the internal combustion engine.
2. Description of Related Art
Recently, in general, with respect to a fuel injection nozzle for an internal combustion engine, such as a diesel engine with high fuel injection pressures, it has been desired to improve a clamping axial force of a clamping member such as a retaining nut in order to ensure a seal during high-pressure conditions between a sealing surface of a nozzle body and that of a nozzle holder.
As shown in FIG. 2, however, when a retaining nut 103 is tightened to clamp a nozzle body 101 and a nozzle holder with each other, a frictional force is developed on a friction generating interface 104 located between a seating surface of a shoulder portion of the nozzle body 101 and an inner seating surface of the retaining nut 103. With this frictional force, the nozzle body 101 twists, so that the cylindricality of a nozzle needle slide portion 105 deteriorates and there is a fear that a defective slide of the nozzle needle 106 may occur. In this case, a countermeasure is to improve the surface smoothness of the inner seating surface of the retaining nut 103. However, it is very difficult to apply a high-degree of surface machining to the inner seating surface of the retaining nut 103 and there arises the problem that the cost increases.
It is an object of the present invention to provide a fuel injection nozzle capable of preventing a defective slide of a nozzle needle by decreasing a frictional force developed between a seating surface of a shoulder portion of a nozzle body and an inner seating surface of a bearing portion of a retaining nut at the time of clamping.
According to an embodiment of the invention, a frictional force reducing member is interposed between a seating surface of a shoulder portion of a nozzle body and an inner seating surface of a bearing portion of a retaining nut to reduce a frictional force developed between both seating surfaces at the time of clamping. With the frictional force reducing member, the frictional force induced between both seating surfaces can be diminished without performing a high-degree of surface machining to the inner seating surface of the bearing portion of the retaining nut, even if the surface roughness of the inner seating surface is large. Consequently, a nozzle needle slide portion can be prevented from being deformed by a twist of the nozzle body which is caused by the frictional force and hence it is possible to avoid a defective slide of the nozzle needle.
Additionally, a flat plate-like member, which has a small frictional coefficient, at least at an end face thereof, located on the nozzle body side, is used as the frictional force reducing member. Furthermore, a metallic member having a hardness equal to that of the nozzle body or the retaining nut can used as the flat plate-like member. Additionally, the flat plate-like member can be a resin member, however, there is a fear of it being melted upon exposure to a high temperature combustion gas. Therefore, a metallic member may be much more advantageous.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.